The present invention relates to the conversion of sodium bromide to hydrobromic acid and sodium bisulfate with improved product quality and improved process economics.
Hydrobromic acid is widely used as an intermediate in the chemical industry. It is utilized in the production of inorganic bromides by reaction with metal hydroxides, oxides, or carbonates; in the production of organic bromides by reaction with alkyl alcohols or alkenes; and as a catalyst for oxidations, alkylations, and condensations in organic chemistry.
In the past, halogenated acids such as hydrobromic acid have been prepared in gaseous form by several laboratory methods such as direct combination of hydrogen and bromide, using platinized silica gel as a catalyst; bromination of organic compounds such as benzene, naphthalene, or tetrahydro-napthalene; and reacting bromine with red phosphorus and water. None of these processes are practical for the industrial production of hydrobromic acid. The first process is generally expensive and presents a considerable explosion hazard. The second process is inefficient and costly in that it typically utilizes only about half of the expensive bromine employed. The last is apt to be violent, difficult to control, and may present a serious explosion hazard.
Currently, there are two main approaches for the industrial production of hydrobromic acid. The first approach is a two conversion process whereby low purity, natural deposits of sodium bromide are converted first into elemental bromine and second into hydrobromic acid. The first conversion is done by oxidation with chlorine, where the sodium bromide is converted into sodium chloride and bromine by the reaction:
2NaBr+Cl2xe2x86x922NaCl+Br2
According to Stanford Research Institute""s Chemical Economics Handbook, commercial bromine suppliers such as Great Lakes Chemicals (located in El Dorado and Marysville, Ak.), Albemarle (located in Magnolia, Ak.), and Dead Sea Bromine Co. (located in Sdom, Israel), currently practice this step. A second conversion involves either burning bromine and hydrogen to form hydrobromic acid, such as discussed in Ullman""s Encyclopedia of Industrial Chemistry, 5th edition, 1985, Volume A4, pg. 396, according to the reaction:
Br2+H2xe2x86x922HBr
or by an electrolytic process whereby a solution of bromine is converted into hydrobromic acid and oxygen (as disclosed in U.S. Pat. No. 4,069,120 to United Technologies Corporation, issued Jan. 17, 1978 and U.S. Pat. No. 4,203,813 to United Technologies Corporation, issued May 20, 1980), according to the reaction:
2Br2+2H2Oxe2x86x924HBr+O2
This two conversion process to produce hydrobromic acid has a number of drawbacks. First, operating and capital costs are high since a separate manufacturing plant is employed for each conversion. In addition, if bromine burning is implemented, free bromine is often present in the hydrobromic acid product, resulting in a product with the characteristic yellow and/or orange color associated with free bromine. This is generally unacceptable for applications requiring a colorless hydrobromic acid product.
The second approach for chemical manufacture of hydrobromic acid is a one conversion process whereby high purity sodium bromide is reacted with sulfuric acid (U.S. Pat. No. 1,379,731 to Lowenstein Radio Corporation, issued May 31, 1921 and U.S. Pat. No. 2,705,670 to American Cyanamid, issued Apr. 5, 1955) according to the reaction:
NaBr+H2SO4xe2x86x92HBr+NaHSO4
This approach is well suited for industrial companies which produce high purity sodium bromide as a by-product and desire hydrobromic acid as a product. However, this approach has a number of drawbacks as well. Operating costs are high if the sodium bisulfate salt is of low purity and therefore has low value. This can occur if (a) there is unreacted sodium bromide in the sodium bisulfate, (b) some of the sodium bisulfate reacts with sodium bromide to produce sodium sulfate, according to the reaction:
NaHSO4+NaBrxe2x86x92HBr+Na2SO4
or, (c) the sodium bisulfate undergoes decomposition to sodium disulfate via the following reaction,
2NaHSO4xe2x86x92Na2S2O7+H2O
Capital costs of the approach are high if the total number of separation steps required to purify the hydrobromic acid and sodium bisulfate are not minimized. Lastly, product quality may also be an issue if low levels of bromine are entrained in the hydrobromic acid via the following reaction,
2HBr+H2SO4xe2x86x92Br2+SO2+2H2O
Generally, entrained bromine is removed from hydrobromic acid by scrubbing with phosphoric acid or by activated carbon.
Therefore, there is a continuing need for an improved process approach for making anhydrous hydrobromic acid and sodium bisulfate. Specific areas for improvement vs. current commercial processes include lowering operating cost, lowering capital cost, and increasing product purity.
It has now surprisingly been discovered that sodium bromide can be converted into anhydrous hydrobromic acid and sodium bisulfate with minimal levels of by-products such as bromine, sodium sulfate, or sodium disulfate by using a one conversion process consisting of a simple reactor and three simple separation processes.
The present invention therefore relates to a process for the conversion of sodium bromide to hydrobromic acid and sodium bisulfate with the following steps:
1) Reaction of sodium bromide and sulfuric acid in a solution of water to produce hydrobromic acid and sodium bisulfate.
2) Separation of hydrobromic acid and water from the sodium bi sulfate
3) Separation of hydrobromic acid from water; and
4) Drying of hydrobromic acid
These and other features, aspects, and advantages of the present invention will become evident to those skilled in the art from a reading of the present disclosure.
All documents cited are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention.